1890; see electrocute + -ion. Meaning "any death by electricity" is from 1940.

electrocute

v.

"execute by electricity," 1889, American English, from electro- + back half of execute. The method first was used Aug. 6, 1890, in New York state, on William Kemmler, convicted of the murder of his common-law wife. Sense involving accidental death is first recorded 1909. Electric chair is also first recorded 1889, which is when the first one was introduced in New York state as a humane alternative to hanging. Related: Electrocuted; electrocuting.